Expo Imaging - Assembly and Testing
How are ExpoDiscs assembled and tested, and why does it matter?
As the inventors of the Digital White Balance Filter, we have always gone to great lengths to ensure the neutrality of the ExpoDisc. Every ExpoDisc is assembled, measured and calibrated to our strict tolerances of colour neutrality and light transmission on a sophisticated transmission spectrophotometer at our facility in California. We test and calibrate each ExpoDisc for 18% light transmission and neutrality in the visible spectrum (400nm to 700nm). The ExpoDisc's 18% light transmission allows the ExpoDisc to be used as an incident ambient exposure tool (as you would with an 18% grey card), as well as for white balance.
The accuracy of a custom white balance depends upon the specific colour characteristics of the material used to set the white balance, in conjunction with the colour temperature of light the white balance is set against. In order to trust a white balance tool in a variety of shooting environments, it must be neutral across the entire visible spectrum. Using a non-neutral tool will introduce a colour cast in your images.
ExpoDiscs are constructed of multiple layers of carefully selected optical grade materials. Because we’ve found that no single material has the same optical characteristics from batch to batch, by incorporating multiple layers of diffusion filters and gels, we are able to compensate for variations in materials and to produce a product which is consistently neutral.
The ExpoDisc's multi-layer design combined with our commitment to testing makes the convenient-to-use ExpoDisc the best white balance tool available